Blog Directory lists by default my network sites correctly, i.e. according to my Site Directory Settings, specifically:
Sort by = Site Name (A-Z)
Listing per page = 20
However, when searching sites, if the results exceed the listing per page setting, the sites are all listed on only one page and are not sorted alphabetically. Moreover, a "next" link is generated on the page which, when clicked, opens a page that states "Invalid page" but is otherwise empty.